In this article
A bonus, an inheritance or a maturing deposit: sooner or later most people hold a single large amount and wonder what it could become. A lumpsum calculation answers that with one formula, and it also shows how much the return rate and the number of years each matter.
The formula
Because the amount is multiplied by the same factor every year, the growth in rupees gets bigger each year even though the percentage is the same. That is compounding.
The three paths start together and fan out. The gap is small at year 5 and enormous at year 30.
The table to keep
| Rate | 10 years | 20 years | 30 years |
|---|---|---|---|
| 8% | ₹2.16 L | ₹4.66 L | ₹10.06 L |
| 10% | ₹2.59 L | ₹6.73 L | ₹17.45 L |
| 12% | ₹3.11 L | ₹9.65 L | ₹29.96 L |
| 15% | ₹4.05 L | ₹16.37 L | ₹66.21 L |
The ringed cell is ₹9.65 lakh, ₹1 lakh at 12% for 20 years. Very high rates like 15% are shown for contrast. They are rarely sustained over decades.
Which matters more: rate or time?
Both. But look at the 10% row: doubling the time from 10 to 20 years multiplies the result by 2.6, and tripling it to 30 years by 6.7. Time has an accelerating effect. Adding years is often the easier lever, because you control it more than the market return.
The last five years add ₹6.6 lakh, more than the first 20 years combined (₹5.7 lakh of growth).
Lumpsum or SIP?
A SIP invests a fixed amount every month. A lumpsum invests everything at once. If you already have the money, the lumpsum starts compounding sooner. If you do not, a SIP builds the habit from your income.
- All ₹6 lakh invested on day one
- Needs the full sum now
- Fully exposed to the market at the start
- Same ₹6 lakh in total, spread over 120 months
- Fits a monthly salary
- Spreads the buying price across market ups and downs
The lumpsum is larger because the money works for longer. But they solve different problems. Most people have a salary, not a spare ₹6 lakh. See start at 25 or 35 for the SIP side.
Real returns are lower than the headline
- Inflation. ₹29.96 lakh in 30 years buys far less than ₹29.96 lakh today. See what ₹1 lakh buys in 2046.
- Tax. Gains are taxed when you sell, at rates that depend on the asset and holding period. Check the current rules.
- Costs. Fund expenses and fees reduce your return a little every year.
- Risk. An average of 12% can hide a −30% year. The order of returns changes what you end up with if you need money at a fixed date.
- Averages versus the CAGR. A 12% simple average and a 12% annual compounded return are different. Read average return vs CAGR.
The rule of 72 shortcut
To estimate how long it takes to double, divide 72 by the rate. At 12% that is 6 years, at 8% it is 9 years. See the rule of 72 for how it works.
Questions people ask
What is the lumpsum formula?
Future value = P × (1 + r)ⁿ, where P is the amount, r is the yearly rate and n is the years.
What will ₹1 lakh be in 20 years at 12%?
About ₹9.65 lakh, if it earns 12% a year compounded annually. Actual returns will vary.
Is a lumpsum better than a SIP?
A lumpsum gets more time to grow if you have the money now. A SIP suits regular income and spreads the buying price. They solve different problems.
How does the rate change the result?
Over long periods a small change in the rate changes the result a lot. At 8% ₹1 lakh becomes ₹10.06 lakh in 30 years, at 12% it becomes ₹29.96 lakh.
Are these returns guaranteed?
No. Market-linked investments move up and down. These figures show how the maths works for a steady rate.